•There has been an explosion at the Fukushima No 1 nuclear power plant in north-eastern Japan, close to the epicentre of the quake. Officials say the blast is not a meltdown but exterior walls of one of the reactor buildings have been destroyed. There are also concerns about Fukushima No 2 plant.

•Tens of thousands of people in the areas surrounding both plants have been urged to evacuate.

•Japanese authorities are preparing to distribute iodine to residents in the evacuation zones to protect them against radiation exposure.

•There are reports of dozens of aftershocks, some as strong as magnitude 6, striking Japan in the wake of Friday's devastating earthquake and tsunami. Japan's state broadcaster has warned people in coastal areas that there could be further tsunamis.

•Around 1,700 people are estimated to have been killed, according to local media reports, but that death toll is expected to rise dramatically. The official death toll now stands at 574, with 586 people declared missing and 1,105 injured.

•Around 10,000 people are missing in the town of Minamisanrikucho in Miyagi prefecture, according to Japanese TV reports.

•More than 215,000 people are in emergency shelters and around 50,000 rescuers have been deployed across the country.

•At least 1.4m homes are without water and around three million are without power.

The full horror of the devastating earthquake and tsunami in Japan is starting to emerge amid fears that the death toll could run into many thousands. A day of high tension saw workers battle to save a nuclear plant from meltdown and 50,000 rescuers fight their way to victims in the midst of mud, flood waters, collapsed buildings and continuing blazes.

At least 1,700 people were reported dead or missing following the earthquake and tsunami, Kyodo news agency said. Further shocks of up to 6.4 magnitude continued to strike the north-east a day and a half after the major quake.

In addition, Kyodo said, 9,500 people could not be contacted in Minami Sanriku in the northern prefecture of Miyagi, around half the population. Japanese broadcaster NHK said 2,700 homes had been destroyed in Arahama, in the same prefecture. Further north, the National Police Agency said 5,000 homes were under water in Rikuzen-Takata, Iwate prefecture. Survivors were reported to be clambering over uprooted trees and overturned cars to reach homes. Rail operators were also searching for four commuter trains that were travelling coastal lines in Miyagi and Iwate when the tsunami struck.

The frantic search for survivors was almost overshadowed by the spectre of radioactive leaks at a nuclear power plant at the heart of the area most affected by Friday's earthquake. At the Fukushima plant, radiation leaked from a damaged reactor after an explosion blew the roof off. Japan's nuclear safety agency said the accident was rated less serious than the Three Mile Island or Chernobyl disasters, but up to 160 people were exposed to radiation.

Authorities told the International Atomic Energy Agency (IAEA), the UN's atomic watchdog, they were making preparations to distribute iodine to people living nearby. Iodine can increase resistance against thyroid cancer in the case of radioactive exposure.

A 20km evacuation zone was imposed around the plant as authorities moved tens of thousands of residents from the area, some 240km north of Tokyo, as they tried to reduce pressure in the reactors. The IAEA said Japanese authorities had informed it of the explosion and that they were "assessing the condition of the reactor core".

Early this morning, technicians were battling to relieve pressure in a second reactor at the plant after its cooling system failed. The procedure was expected to release a small amount of radiation.

As the first wave of military rescuers began arriving, prime minister Naoto Kan said 50,000 troops had joined rescue and recovery efforts, aided by boats and helicopters. Dozens of countries also offered help; Britain sent a specialist team of search and rescue experts. Andrew Mitchell, the international development secretary, said: "Our thoughts are with the people of Japan as they begin to recover from this terrible disaster."

Barack Obama pledged US assistance following what he called a potentially "catastrophic" disaster.

In a day of chaos, 300,000 people were evacuated from their homes in the region due to radiation and tsunami fears and quake damage. Two hundred fires had been sparked, including three that still raged in the north-east city of Kesennuma, Kyodo said. In the city of Shiogama, oil was leaking from a refinery into the harbour.

Friday's 8.9 magnitude shock, the fifth most powerful quake in a century, appeared to have moved the main island of Japan by three metres and shifted the Earth on its axis, an expert with the US Geological Survey told CNN.

As temperatures dropped to freezing in the worst-hit north-east prefectures, survivors huddled in shelters and braced themselves against more tremors. While many remained calm, some clutched friends and sobbed as the extent of the disaster sank in. TV footage showed rescue helicopters winching children and adults to safety from the wreckage. Many could be seen trapped on rooftops.

The city of Sendai remained swamped by water. Fishing boats, cars and buildings were stranded across farmland along the north-east coastline. "Everything is so hard," said Kumi Onodera, a 34-year-old local, who described her ordeal as "like a scene from a disaster movie. The road was moving up and down like a wave. Things were on fire and it was snowing [ash]."

Long queues formed outside shops in towns near the coastline as people cleared shelves of water and food. At least a million people in the north-east of the country were thought to be without drinking water. Five million homes are without power and electricity providers have warned they will need to impose rolling blackouts in parts of Tokyo.

There was worldwide consternation at the prospect of a nuclear meltdown in the wake of the Japanese earthquake. Tens of thousands of people took part in an anti-nuclear demonstration in southern Germany. The event had been planned for some time, but after the news of Japan's nuclear emergency, organisers were overwhelmed by some 50,000 people who turned up to take part.

The demonstrators, who stretched in a 45km chain from Neckarwestheim power plant to the city of Stuttgart, were demanding that the German government move away from nuclear power.

In the UK, energy secretary Chris Huhne said that the government was monitoring the nuclear situation in Japan. "It's too early to say what the cause was, let alone what the implications are," he added.

Japan nuclear crisis worsens as country braces for second huge earthquake• Scientists predict second massive quake of 7.0
• Nuclear crisis as second reactor cooling system fails
• PM says disaster is worst since second world war
• Earthquake and tsunami death toll set to top 10,000

Three days after a devastating earthquake unleashed a tsunami in which at least 10,000 people are feared dead, Japan on Sunday faced a deepening nuclear crisis and the prospect of another very powerful quake.

The prime minister, Naoto Kan, called the disaster "Japan's most severe crisis since the war ended 65 years ago". He called on the country to unite and said its future would be decided by the response to this crisis.

The threat of further seismic shifts and tsunami is far from over. As rescue teams from more than 70 countries and tens of thousands of Japanese troops descended on the disaster zone, meteorological agency officials warned there was a 70% chance of a magnitude 7.0 earthquake striking the region in the next three days. "There will be many aftershocks in multiple locations. We have to brace ourselves for aftershocks of magnitude 5 or even magnitude 6," an agency official said.

The meteorological agency upgraded last Friday's earthquake, the fifth biggest in the world for a century, from magnitude 8.8 to 9.0. What began as a violent seismic shift lasting minutes has left a permanent geological legacy: the US geological survey said the force of the quake had shifted the island a distance of 8ft (2.5 metres).

New images from Japanese TV revealed, one submerged community after the other, the full extent of the devastation, and the determination of a nation united by a natural catastrophe that almost defies comprehension.

Rescue teams and survivors are in constant fear of yet more powerful quakes and tsunami. Millions of others were bracing for a potentially catastrophic nuclear accident after the government warned that a second nuclear reactor at the Fukushima Daiichi (No 1) nuclear power plant could explode.

More than 300,000 people are living in emergency shelters along the coastline and millions of survivors face a third night without water, electricity and proper food. Japanese media reported that 5.5 million people were without power, while 20,800 buildings had been destroyed or damaged.

Land once occupied by towns and villages now resembles paddy fields, the surface of the water breached by the roofs of wrecked homes, trees and other debris created by a wall of water so high that taking refuge on a building's third floor proved futile for some.

The arrival of Japanese TV crews in the worst-affected areas has given the disaster what it lacked in the immediate aftermath: a human face.

Residents broke off from searches for lost friends and relatives, and some spoke from hospital beds to recount the terror of Friday afternoon. "Everything has turned upside down," an elderly man in Miyagi prefecture said. "After the tsunami, everything had gone. But we're going to have to get on with life."

Fighting back tears, one woman said: "I tried to run away but I was just swallowed up by the tsunami. I kept shouting 'Save me, save me'. I can't begin to describe what I saw."

Another evacuee from Miyagi said: "My children are cold and complaining of headaches. We don't know how long we're going to have to stay here. It's very upsetting."

The official death toll has reached more than 700, with more than 10,000 others still missing. Given the size of the disaster, in breadth and intensity, the eventual number of dead could be much higher.

The apocalyptic images of entire neighbourhoods filled with the muddy remnants of the tsunami suggest that there is little hope that many, if any at all, will be found alive.

In Rikuzentaka, a city close to the coast, some among the 1,000 people taking refuge at a school located on high ground wept as they stared at a list of the survivors. "There have been tsunami before but they were just small. No one ever thought that it could be like this," said Michiko Yamada, a 75-year-old in Rikuzentakata, a near-flattened village in far-northern Iwate prefecture.

Images taken from the hills overlooking Kesennuma, in Miyagi prefecture, showed a town of more than 70,000 reduced to ashes by fires that raged on Friday night.

In scenes repeated along the coast, debris hangs from tree branches well inland, indicating how high the waters surged before they began to recede. One image, broadcast across the world, shows a solitary white car perched on the roof of a house.

All other news has been pushed aside while the country's broadcast media feeds an insatiable public need for information about the death toll and the nuclear crisis in Fukushima.

With alarming frequency, broadcasts are punctuated with a now-familiar jingle announcing more powerful aftershocks that snake their way down from the northeast to Chiba and Tokyo.

While Nagatacho, Japan's political nerve centre, has united around the rescue and relief effort, criticism of the authorities' response is seeping through. A headline in the Asahi Shimbun blasted the government's "incoherent" crisis management strategy, accusing it of taking too long to release information about the problems at Fukushima nuclear plant and evacuate tens of thousands of people living nearby. "Every time they urged us to 'stay calm' without providing concrete data, they simply made people more anxious," the paper quoted an unidentified politician as saying.

The cost of the rescue, relief and recovery effort will be huge. Manufacturers have closed plants while the energy infrastructure, from closed or crippled nuclear plants to burning oil refineries, is so badly damaged that power companies have warned of sporadic electricity cuts in areas hundreds of miles from the epicentre.

Russia, a rival for new energy sources in the Asia-Pacific, on Sunday offered to provide emergency supplies of natural gas.

The government, meanwhile, is poised to dip into a 200bn yen (£1.5bn) contingency fund to pay for the relief effort.

The prime minister, Naoto Kan, until Friday the subject of a funding scandal that could have cost him his job, called on the country to come together in its time of need. "We must do all we can to save as many people as possible," he said.

That effort is now an international concern, with the arrival over the weekend of rescue and medical teams from several countries, as well as a US aircraft carrier.

A team of 63-strong British rescue workers, some fresh from searching through the rubble in Christchurch, was due to land in Tokyo, along with two search dogs and 11 tonnes of equipment, including heavy lifting and cutting gear.

• The Japanese prime minister has called the disaster the worst crisis since WWII. There are also reports that up to 10,000 are feared dead in the Miyagi prefecture alone.

• The original earthquake to hit Japan has been upgraded to a magnitude of 9.0 by the Japanese authorities (the US Geological Survey has not made the same change).

• The struggle to control a nuclear crisis at two power stations continues. Officials said there is a risk of a second explosion at the Fukushima power station but Yukio Edano, chief cabinet secretary, said the facility could withstand the impact. Technicians are battling to cool a third reactor after a blast at reactor one on Saturday. Technicians are pumping sea water into the reactor in a bid to prevent a nuclear meltdown. There are also unconfirmed reports that a cooling system pump has stopped operating at Tokai No. 2 Power Station, a nuclear power plant, in the village of Tokai, Ibaraki Prefecture.

• More than 250 aftershocks have rocked Japan since the original earthquake on Friday. The US Geological Survey said 30 of these were in excess of magnitude 6. Japan's meteorological agency said there was a 70% chance of a magnitude 7 aftershock striking in the next three days.

• The huge rescue effort now includes 100,000 Japanese soliders, around 40% of its armed forces. International rescue teams are heading towards the region including a UK team. Tokyo's vice-mayor said 44,000 meals of crackers, 643,000 of instant rice and 57,000 units of condensed milk are on their way to the disaster area, along with 384,000 blankets and 9000 portable toilets.

• Stories of rescues and tragedies are beginning to emerge, including from Hiromitsu Shinkawa, a 60-year-old man rescued after being swept out to sea with only his roof as a makeshift raft.

• A volcano in southern Japan has resumed its eruption after a two week break. It is not clear whether this is connected with the earthquake on Friday.

Japan's Shift

Images from NASA's Terra satellite show the coastline of Japan's Honshu island in the area around Sendai before and after Friday's earthquake. The left image is from Feb. 26, and the right image is from today. The images are color-coded to reflect surface composition rather than what the eye would see. The "Flood" label helps you gauge the extent of the flooding caused by the tsunami that followed the quake.

This week's earthquake caused the main island of Japan to shift as much as 13 feet to the east, seismologists say. That may sound like a shocker, but it's just one of the natural changes that come along with an 8.9-magnitude temblor — like the 1.6-microsecond speed-up of Earth's daily rotation and the 4-inch shift in Earth's axis.

The eastward shift was documented by Japan's Geonet network of GPS monitoring stations, based in Tsukuba, said Ken Hudnut, a geophysicist at the U.S. Geological Survey's Earthquake Hazards Program in Pasadena, Calif. Similar shifts took place during last year's 8.8 earthquake off the Chilean coast, as well as the 9.1 earthquake near Sumatra that caused a disastrous tsunami in 2004.

"It's the same phenomenon in all three cases," Hudnut said. The movement is linked to the release of the strain that builds up when one tectonic plate grinds against another in a subduction zone.

"What's going on is that the plate going down drags along with it the upper plate as strain is stored in between earthquakes," he explained. "When the earthquake occurs, the upper plate lurches eastward over the subducting plate. The oceanic plate that's going down is relatively rigid, but the upper plate is like a wedge of material that's more elastic. So picture that upper wedge as being almost like an accordion that's being compressed between the times of earthquakes. It's like a spring. You're loading up the spring between earthquakes — in other words, you're compressing the eastern edge of the spring toward the main island of Japan. The earthquake allows that material to spring out toward the east."

Japan's network of 1,200 GPS monitoring stations, operated by the Geographical Survey Institute, shows a maximum springing-out effect of 13 feet (4 meters), with an average displacement of about 8 feet (2.5 meters) along a stretch measuring more than 300 miles (500 kilometers).

Everything that links GPS readings to maps, ranging from driving directions to property records, will have to be changed as a result of the shift, Hudnut told me. "Their national network for property boundary definitions has been warped," he said in an e-mail. "For ships, the nautical charts will need revision due to changed water depths, too (of about 3 feet). Much of the coastline dropped by a few feet, too, we gather."